1. Field of the Invention
The present invention relates to monitoring chemicals in a process chamber using a spectrometer having a plasma generator, based on patterns over time of chemical consumption. The relevant patterns may include a change in consumption, reaching a consumption plateau, absence of consumption, or presence of consumption. In some embodiments, advancing to a next step in forming structures on the workpiece depends on the pattern of consumption meeting a process criteria. In other embodiments, a processing time standard is established, based on analysis of the relevant patterns. Yet other embodiments relate to controlling work on a workpiece, based on analysis of the relevant patterns. The invention may be either a process or a device including logic and resources to carry out a process.
2. Description of Related Art
Semiconductor manufacturing has adopted various telemetry techniques utilizing mass spectrometry or spectrographic analysis to improve the cleaning, conditioning or operation of reaction chambers in which a variety of reactions take place, such as deposition, cleaning, etching, implantation, ashing, etc. Telemetry techniques help operators monitor processes that take place on a microscopic level inside a closed chamber that often is sensitive to any form of outside radiation. One technology sometimes used is monitoring a plasma reaction chamber to view radiation emitted by process plasma. Another technology is to use a mass spectrometer to analyze residual gases. More recently, these inventors have begun using a spectrometer having a plasma generator to analyze process gases.
One area of process analysis interest is the efficiency of a chemical reactor and its ability to transform feed gases (which themselves may not be reactive) into reactive species, which can undergo and/or produce desired chemical changes. In a plasma etcher, the action of the plasma may convert stable, otherwise unreactive feed gases into reactive chemical atoms and radicals that then remove surface materials on the substrate to be etched. An example is the plasma breakdown of unreactive CF4 into highly reactive F atoms, which remove Si, SiO2, and/or Si3N4 from the surface of silicon wafers. In plasma-assisted deposition, the plasma may assist in breakdown of a precursor such as TaCl5 into Ta atoms, which are deposited onto a semiconductor surface.
Chemical conversion efficiency, sometimes called “chemical utilization” is rarely measured, because of the difficulty of making proper chemical measurements.
Another area of interest is monitoring of atomic layer deposition (ALD), also known as alternating layer deposition. ALD is a method of depositing thin films of materials onto substrates, including the fabrication of semiconductor electronic devices. As opposed to more conventional deposition methods (e.g. Chemical Vapor Deposition—CVD, or thermal film growth), in which the important steps of film formation (e.g. adsorption of precursor species onto the substrate, followed by chemical reaction steps of the adsorbed film) occur simultaneously, ALD breaks the steps into separate, discrete processing steps, in order to achieve preferred film properties. These properties may include step coverage, across-wafer uniformity, and reduced film contamination. The ALD process can be carried out at lower substrate temperatures than other deposition processes, which is useful generally and, in particular, in temperature-sensitive processes.
A related area of interest is detection of air leaks into a process chamber. One process for leak detection is described in “Air Leak Evaluation of a Production Dry Etcher by Means of Optical Emission Spectroscopy”, F. Ciaovacco, S. Alba, F. Somboli, G. Fazio, AEC/APC Symposium XIV, 2002. The technique described requires a plasma in the process chamber to cause emission of light with a wavelength attributed to CN. The CN is formed by chemical combination in the plasma of carbon atoms from a flow of carbon-containing feed gas, e.g. CF4, which has been admitted to the reaction chamber for this purpose and N atoms from N2 molecules in the air leak. The described technique is applied to a plasma reaction chamber, using a window to observe emissions from the plasma. The technique described does not work with non-plasma process chambers where there is no ionization.
Given the anticipated desire for improved process control, a process and related device that addresses any or all of the areas of interest above and/or related areas of interest would be well received. A workable telemetry process would create an opportunity to improve manufacturing process performance.